The present invention relates to a golf ball including a layer containing fillers, and more particularly to a golf ball with a layer containing exfoliated graphite nanosheets.
Conventional golf balls typically comprise two functional components: a core and a cover. The primary purpose of the core is to be the xe2x80x9cspringxe2x80x9d of the ball or the principal source of resiliency. The cover protects the core and provides feel and greenside performance.
Two-piece solid balls are typically made with a solid core, usually made of a cross-linked polybutadiene or other rubbers, encased by a hard cover material. The core and/or the cover may also comprise multiple layers.
In an effort to make golf balls with improved performance characteristics, manufacturers have added fillers in various layers of the multi-piece golf balls. Fillers are typically added to adjust the density, rotational moment of inertia, flex modulus, mold release, or the melt flow index of one or more layers. For example, adding fillers to thermoplastic layers increases the flexural modulus or stiffness of such layers, so that the golf balls may achieve lower spin rates and greater distances.
Fillers used in the golf ball art typically include fibers, inorganic powders, carbonates, metal and metal alloys, metal oxides, metal stearates, particulate carbonaceous materials and micro balloons. Fibers typically include glass fibers, aramid fibers and asbestos. Inorganic materials typically include silica, clay, talc and mica. Metal and metal alloys typically include titanium, tungsten, aluminum, bismuth, nickel, molybdenum, iron, steel, lead, copper, brass, boron, zinc and tin, among others. Metal oxides typically include zinc oxide, iron oxide, aluminum oxide, titanium oxide and magnesium oxide. Metal stearates typically include zinc stearate, calcium stearate, barium stearate, lithium stearate and magnesium stearate. Particulate carbonaceous materials typically include graphite, carbon black, natural bitumen, cotton flock and cellulose.
The fillers are typically mixed or blended in a finely divided form with polymeric material, or are mixed with the monomers prior to polymerization to react and become part of the polymer. However, some of these fillers, such as graphite, have nanostructures that have not been fully utilized in the golf ball art. Up to now, graphite is typically delaminated into single-layer platelets with various aspect ratios for dispersion into a polymeric matrix for use as a layer(s) on the golf ball. Hence, there remains a need in the art for a golf ball having improved filled layers.
The present invention is directed to a golf ball having at least one layer that comprises fillers having nanostructures.
The present invention is also directed to a golf ball having at least one layer that comprises fillers having altered nanostructures.
The present invention is also directed to a golf ball having at least one layer that comprises exfoliated graphite.
In accordance to one aspect of the invention, at least a layer in the golf ball contains nanosheets of exfoliated graphite dispersed in a polymeric matrix. Exfoliated graphite is graphite that has been intercalated preferably by an oxidation process, where the atoms or molecules have been inserted into the inter-planar spacing between the layered planes of carbons, and expanded. The intercalated graphite is expanded or exfoliated preferably by brief exposure to high heat to expand the thickness of the graphite. The expanded or exfoliated graphite is then mixed with monomers and polymerized in situ to form a polymer with a network of nanosheets of the exfoliated graphite dispersed therein. The exfoliated graphite advantageously retains its nanostructure during the polymerization process. The resulting golf ball layer comprising such polymer with nanosheets of exfoliated graphite exhibits superior tensile strength, low permeability to gas and increased impact strength.
In accordance to another aspect of the invention, the expanded or exfoliated graphite is compressed together into flexible thin sheets or foils. Such sheets can be made with or without a polymeric binder. Such flexible foils of compressed exfoliated graphite exhibit low gas permeability property. The present invention is also directed to a golf ball comprising a water vapor barrier layer, wherein the water vapor barrier layer comprises a foil of compressed exfoliated graphite layer.